Ornithopoda

Ornithopods Temporal range: Middle Jurassic - Late Cretaceous, 164–66 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Seven archetypal ornithopods (top to bottom): Ouranosaurus, Tenontosaurus (background) with Convolosaurus (foreground), Muttaburrasaurus, Edmontosaurus annectens, Dryosaurus altus, Corythosaurus casuarius
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Dinosauria
Clade:	†Ornithischia
Clade:	†Cerapoda
Clade:	†Ornithopoda Marsh, 1881
Subgroups
†Ampelognathus? †Burianosaurus †Changmiania? †Convolosaurus †Gideonmantellia? †Elasmaria †Hypsilophodontidae? †Iguanodontia Baur, 1891 †Cumnoria †Napaisaurus †Rhabdodontomorpha †Dryomorpha Sereno, 1986 †Hesperonyx †Dryosauridae †Ankylopollexia
Synonyms[1]
?Clypeodonta? Norman, 2014 ?Euornithopoda Sereno, 1986 ?Hypsilophodontia Cooper, 1985

Ornithopoda (/ˌɔːrnəˈθɒpədə/)^[2] is a clade of ornithischian dinosaurs, called ornithopods (/ˈɔːrnəθəˌpɒdz, ɔːrˈnɪθ-/).^[3][4] They represent one of the most successful groups of herbivorous dinosaurs during the Cretaceous. The most primitive members of the group were bipedal and relatively small-sized, while advanced members of the subgroup Iguanodontia became quadrupedal and developed large body size. Their major evolutionary advantage was the progressive development of a chewing apparatus that became the most sophisticated ever developed by a non-avian dinosaur, rivaling that of modern mammals such as the domestic cow. They reached their apex of diversity and ecological dominance in the hadrosaurids (colloquially known as 'duck-bills'), before they were wiped out by the Cretaceous–Paleogene extinction event along with all other non-avian dinosaurs. Members are known worldwide.